Tuberculosis and HIV: Background Information

Treatment of Latent TB

Usually a long course (between six and nine months) of the antibiotic isoniazid is prescribed. Treatment is prolonged because antibiotics work when the TB-causing bacteria are dividing, and in the case of latent TB, these bacteria grow very slowly.

Treatment of Active TB

Due to widespread use of antibiotics and other factors, including improper adherence to therapy, TB-causing bacteria have developed varying degrees of resistance to therapy. In high-income countries like Canada, the U.S., Australia and Western Europe, once the diagnosis of active TB is made, it is often standard procedure to have a fluid sample (from the lungs or other affected tissue) taken and the TB bacteria tested in the lab for their ability to resist antibiotics.

Treatment of TB has two goals:

• to improve the health of people with TB by curing them of this infection
• to make patients non-infectious

The most common first-line treatment of active TB is a combination of the following antibiotics:

• isoniazid
• rifampin
• pyrazinamide
• ethambutol

In HIV-positive people, doctors initiate potent combination therapy for HIV (commonly called ART or HAART) as soon as possible once TB has been diagnosed, as this helps improve the chances of recovery and survival. Doctors may also have to adjust antibiotic regimens or ART to reduce potential drug-drug interactions.

HIV-positive people co-infected with TB are at risk for developing IRIS -- immune reconstitution inflammatory syndrome. This occurs because when ART is initiated, the immune system is strengthened and begins to recognize and fight germs that it previously was unable to fight. As a result, symptoms of an infection (such as TB) may temporarily appear or may temporarily grow worse. Symptoms of IRIS can appear anywhere from two weeks to two years after ART has been initiated and are inflammation related. These can include fever, swollen lymph nodes and other symptoms depending on the type of infection and organ affected.

In some cases, such as in TB-related IRIS, drugs such as corticosteroids may be prescribed to help reduce symptoms caused by inflammation. IRIS tends to occur in people who have very low CD4+ counts (less than 50 cells).

Additional antibiotics for the treatment of TB are available, but these, particularly second-line agents, tend to have more side effects, must be injected and may require extended courses of therapy. This is the case when treating multi-drug resistant (MDR)-TB.

New antibiotics for the treatment of TB are being tested.

Future CATIE publications will feature developments about TB and HIV.

References

1. O'Donnell MR, Saukkonen JJ. Chapter 168. Antimycobacterial Agents. In: Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson JL, Loscalzo J, eds. Harrison's Principles of Internal Medicine. 18th ed. New York: McGraw-Hill; 2012.
2. Raviglione MC, O'Brien RJ. Chapter 165. Tuberculosis. In: Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson JL, Loscalzo J, eds. Harrison's Principles of Internal Medicine. 18th ed. New York: McGraw-Hill; 2012.
3. Fauci AS, Lane HC. Chapter 189. Human Immunodeficiency Virus Disease: AIDS and Related Disorders. In: Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson JL, Loscalzo J, eds. Harrison's Principles of Internal Medicine. 18th ed. New York: McGraw-Hill; 2012.
4. Ershova JV, Kurbatova EV, Moonan PK, et al. Acquired resistance to second-line drugs among persons with tuberculosis in the United States. Clinical Infectious Diseases. 2012 Dec;55(12):1600-7.
5. Yee DP, Menzies D, Brassard P. Clinical outcomes of pyrazinamide-monoresistant Mycobacterium tuberculosis in Quebec. International Journal of Tuberculosis and Lung Disease. 2012 May;16(5):604-9.
6. Fox W, Wiener A, Mitchison DA, et al. The prevalence of drug-resistant tubercle bacilli in untreated patients with pulmonary tuberculosis; a national survey, 1955-56. Tubercule. 1957 Apr;38(2):71-84.
7. Keshavjee S, Farmer PE.Tuberculosis, drug resistance, and the history of modern medicine. New England Journal of Medicine. 2012 Sep 6;367(10):931-6.